Résumé
In order to determine the origin of optical limiting in singlewall carbon nanotube (SWNT) suspensions, we carried out Z-scan and pump-probe experiments at 532 nm and 1064 nm, for different input energies. We evidenced strong nonlinear scattering due to heat transfer from the carbon nanotubes to solvent which induced solvent bubble growth and a nonlinear refractive effect. We noticed similar comportment at 1064 nm and at 532 nm, but with a lower bubble growth threshold at 532 nm. At the microsecond timescale, we evidenced cavitation bubbles. We also evidenced, via emission studies, a phase change corresponding to optical limiting threshold, which we associated to carbon nanotube sublimation. Optical limiting performances of water and chloroform suspensions were compared and solvent effects are discussed.